Method of producing shell roof structure



Aus. 2, 1966 A. T. BROWN 3,263,322

METHOD OF PRODUGING SHELL ROOF STRUCTURE Filed Jan. '7, 1959 5 Sheets-Sweet l T 6 T s 6 5 .-521 J5 5 V 'Tf'- f. L 7 j 52'/ INVENTOR. Arthur T. Bro wn Aug- 2, 1966 A. T. BROWN 3,263,322

METHOD OF PRODUCING SHELL ROOF STRUCTURE Filed Jan, 7, 1959 5 Sheets-Smet 2 111 zz) 26W WHVJM (plm, T MUM.; .Y M ,L *A Y. v-.L1 fr v l l 55 my S (Z5 27 B IN VEN TOR. Arthur T Brown Aug. 2, 1966 A. T. BROWN 3,263,322

METHOD OF PRODUCING SHELL ROOF STRUCTURE Filed Jan. 7, 1959 5 Sheets-Smet 5 IN VENTOR. Arthur T. Brown BY A l United States Patent O 3,263,322 METHOD OF PRDUCING SHELL ROOF STRUCTURE Arthur T. Brown, 726 N. Country Club Road, Tucson, Ariz. Filed Jan. 7, 1959, Ser. No. 785,466 2 Claims. {CL 259-446) My invention -relates to an improved shell roof-type structure. It relates more in particular to Ian improved structure and method of forming the same wherein the completed roof or the like resulting from the practice of the method comprises a hyperbolic paraboloid.

The common method of producing roof structuresand by roof structures I include not only the roof portion of domestic and commercial buildings but porticolike structures in which a roof is supported by columns `to form an outdoor shelter-is to place struts, trusses and the like on supporting walls, provide `a series of rafters supported by ,the struts or other truss members, and lay a roof on the rafters. The roof itself, therefore, does not in any way support its own weight except for the portion thereof which lies between the rafters which form the main support. A less common method of building a roof is to `form a shell structure which not only comprises the roof but which also furnishes its own support. Typical of a shell structure would be a roof cornprising `a section of a sphere, a section of an ovate body, or a section of some other type of curved structure which by its very shape distributes stresses throughout substantially its entire surface and therefore can support itself.

One of the principal problems associated with the use of a shell structure for roofing purposes is the relatively high labor cost and the relatively high degree of skill which is required to produce the forms for casting the roof. Within the last 50-100 years, however, architects and builders have gradually improved and simplified the method of producing shell roofs, but still the degree of skill and the amount of labor involved have continued to be such that the use of shell roofs in the United States has not been extensive even though in parts of Europe, particularly in the Mediterranean countries, there has been a considerable advance in the use of this particular design.

One of the modified shell structures which has greatly simplified the production of the necessary forms for casting it is the hyperbolic paraboloid shell in which a section running either straight longitudinally or straight transversely of the shell forms a straight line. This makes it possible to lay a series of straight forms, such as specially shaped timbers, and gradually rotate them `about a designated center line to form a structure which in oblique section comprises a parabola. Using this and other type shells, 'a reinforced concrete roof form 2-4 inches thick can be used to span :as much las 200 feet without support except at its edges. These types of structures can also be used to produce overhangs of 50 feet or more by supporting them only along one edge.

Notwithstanding the marked advances in shell structures in the last few years advances which have permitted their successful use in the United States where labor costs .are relatively much greater than in European countries the latest designs still cannot be used effectively not only because of their cost but because of the high technical skills required both on the part of the architect who designs the roof and the builder who executes the design. Actually the skills are lof such an order that in almost all instances where shell roofs have been successfully employed the same highly skilled person who designed the roof also has been responsible for its construction.

The principal of my invention is the provision of an improved shell roof structure.

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Another object is the provision of a shell roof structure which can be produced by relatively unskilled craftsmen and which can be put together without the use of special techniques and materials.

Still another object is the provision of a shell roof structure having great flexibility in design and which may be employed in relatively small installations and in installations requiring provision of -a large covered area.

A still further object is the provision of a shell roof structure which may be used for conventional buildings employing commonly available forms and materials,

Other objects and features of my invention will be made apparent in the following detailed description taken with the accompanying drawings, wherein:

FIG. 1 is a plan view showing one form of roof produced in accordance with my invention;

FIG. 2 is a fragmentary front elevational view thereof;

FIG. 3 is a side elevational View;

FIG. 4 is an enlarged fragmentary sectional view taken on the line 4 4 of FIG. l;

FIG. 5 is `a transverse sectional view taken on the line 5 5 of FIG. 1;

FIG. 6 is a transverse sectional view taken on the line 6 6 of FIG. l;

FIG. 7 is an enlarged fragmentary sectional view taken on the line 7 7 of FIG. 1;

FIG. 8 is an enlarged fragmentary sectional view taken obliquely along the line 8 8 of FIG. 1;

FIG. 9 is a perspective View showing a gusset strip employed to join the two :sections of the roof comprising FIG. 1;

FIG. 10 is a plan view showing one manner in which strip material comprising a portion of the shell roof ,may be secured together;

FIG. ll is a greatly enlarged fragmentary sectional view showing the manner in which the members comprising the shell roof are secured together;

FIG. 12 shows another form of shell roof embodying the features of my invention circular in form and adapted `for special types of design such as in the production of a ramada;

FIG. 13 is an elevational View of the roof design shown in FIG. 12;

FIGS. 14 and 15 are modified views similar to FIGS. 7 and 8, respectively, showing one manner in which the shell roof of my invention may be modified for decorative or the like reasons.

In producing the improved roof structure: `of my invention I take advantage of the principle developed in the production `of concrete shell roofs of the hyperbolic paraboloid type, namely, the fact that even though the shell roof structure is curved, a section taken in a given direction and a section perpendicular to said first-mentioned section both comprise straight lines. Utilizing typically a uniformly corrugated sheet of steel, a hyperbolic paraboloid can Ibe formed by grasping opposite edges Iof such corrugated sheet so as to embrace the outside corrugation on each side and twisting such edges in opposite directions. If two such sheets are placed in contact with each other with the corrugations running in opposite directions that is to say, with the corrugations of one sheet at right angles to the corrugations of the Iother sheet and any two opposite sides moved rotatably in opposite directions, the hyperbolic paraboloid shape will be retained if contiguous portions `of the two sheets are secured together by welding, riveting, brazing, soldering or the like. The nurn-ber of sheets employed in this manner should be at least two but optionally can be three, four, or any number depending upon the material comprising the sheet, its thickness, the type of corrugation, and the extent of the span which is required.

It is of course obvious that, while relatively thin sheet steel or sheet aluminum or other relatively inexpensive, commonly available material can be used to advantage, sheet plasticA and sheets of .other type materials may also be use-d without departing from the spirit and scope of the invention. In the specific embodiments of the invention shown in the drawings and described hereinbelow, the principal material comprising the shell is sheet metal having a uniform type of corrugation of generally rectangular cross section `so that the amount of surface in contact is relatively extensive. In order to illustrate the invention, the cor-rugations have been shown relatively large with respect to the remaining physical dimensions. I have used successfully commonly available corrugated sheet steel and aluminum in producing shell roofs of the type described herein in which the corrugations are very much smaller with respect to the length and breadth of the sheet than would appear from the illustrative drawings.

Referring now rst to FIGS. 1-9, the shell roof there shown comprises two generally identical sections A and B each comprising a top corrugated sheet 21, a middle corrugated sheet 22, and a bottom corrugated sheet 23. Each of the sections A and B comprises a hyperbolic paraboloid, the three corrugated sheets 21, 21 and 23 being twisted in the manner described hereinabove and secured to one another at points of contact by rivets 24 as shown in FIG. 1l or by other suitable fastening means such as spot welding. As the two elevations and several sections of FIG. 1 show, all the exterior edges of the sections comprise straight lines as do also all sections taken either directly transversely or .directly longitudinally of FIG. l. Each of the sections, however, is curved running from corner to corner as FIG. 8 shows, so that the two sections taken together flare up at the center as shown in the front elevation in FIG. 2 and down at the sides; but at the rear portion of the roof the opposite situation exists, namely, the roof is lowest where the two sections meet at its rear and highest at the two outside edges.

While each of the sections A and B could comprise a separate roof, they are in fact joined together along their contacting edges by an upper gusset strip 26 and a lower gusset strip 27. The gusset strips 26 and 27 may be secured to the sections by any suitable means such as riveting, welding `or the like. Illustratively the roof structure shown in FIG. 1 is supported by three posts or pillars 28, 29 and 31, the post 29 being common to the two sections A and B and the other two posts supporting the sections A and B, respectively, at their lowermost outside corners. The posts or pillars 28, 29 and 31 may of course comprise any conventional .structural -support member such as a portion of a load-bearing wall, a buttress or the like, and they may comprise vertically extending members or obliquely extending members depending upon the architectural `design of the structure with which the roof is associated. The roof of my present design may also be supported at one edge so that its entire area represents an overhang as is sometimes done with shell structures. Since it is obvious that any of the usual architectural treatments may be used, I have not deemed it necessary to show more than one type of support. The posts 28, 29 and 31 are `of course suitably anchored at their lowermost ends by practices common in the building industry, and the roof is attached to the tops of the posts by suitable means such as gusset plates 32 which are secured by welding, riveting, bolting, or the like to both the supporting members and the roof structure. Depending upon the manner in which the roof structure is employed, side edges of the roof sections A and B may be left open or a sealing strip 33 may be secured around the edges as shown particularly in FIGS. -7.

It should be noted that water falling on the roof itself will divide substantially along a line running through opposite corners of each of the sections A and B so that half the water would run to the outside of the roof and half to the inside in each instance for overow at the lowermost point of the section of the roof receiving Cil such water. Usual types of gutters, down spouts, and the like may be employed if desired to control s-uch water flow. It should be noted also that any water which might by chance enter the space between the sections 21, 22 and 23 will flow along the bottom :gusset strip 27 and be discharged at the lowermost cen-ter portion of the roof in alignment with the post or support 29.

As pointed out hereinabove, there is no theoretical limit to the area which may be covered by a roof produced in accordance with my invention; and, in general, regular commercially available materials may be employed. Notwithstanding the fact that for the purpose of improving features of the roof of my design I may have specially designed structural members produced such as special shapes of corrugated materials, to avoid the necessity of specially `fabricating large sheets of corrugated material which are diicult `to ship, a plurality of strips of corrugated material 136 as shown in FIG. 10 may be overlapped at their edges and secured together as by welding to form a :rectangular sheet 121 having the overall dimensions lof the top sheet 21 shown in the main embodiment. A roof formed of materials of this type can in all other respects employ the features shown in FIGS. 1-9.

In connection with FIG. 1 I have pointed out that the roof sections A or B could themselves comprise complete roofs. It is of course obvious also that a roof formed of a single set of superposed corrugated sheets may have substantially any plane shape which an archi- Itect may desire to use in a given structure. By taking a roof section such as A in FIG. l, for example, and cutting out a circle, 4ovate, or other sha-pe but otherwise leaving the sheets secured together, a modified style 0f roof would result; and while the salme structural features would be employed, its appearance would be markedly different. Illustratively I have shown in FIGS. 12 and 13 a completely circular roof 'formed by four sections 37, 38, 39 and 40 each comprising two right angular sides and one subtending arcuate side, so that the arcuate sides of the four sections combine to form a circle. Each ot these sections may be formed of two :or more sheets of corrugated material overlapped, mutually deformed and secured together as in the preferred embodiment. Each of the sections 37-40 may be considered as being identical with a square section in which an arcuate line is cut from opposite corners, the arc being dened by generating a circle about a third corner whose axis or radius is equal to the width of one of the sides. The four sections comprising the structure shown in FIGS. 12 and 13 are secured together -at their contiguous edges by gusset strips 41 and 42 similar to `the corresponding gusset strips in the first-described embodiment, and the composite yroof is supported on four pillars 43. These supports are contiguous with the matching edges of the four sections at the lowermost portion of their curvature. The highest point of curvature in this design is at the apex where the four sections come together. The curved portion of the edge between the supports 43 is generally at an intermediate height between the points of attachment of the roof to the supports 43 and the center apex. It should be noted that of the curved portion of each of the sections between the supports 43 were to continue out to form a rectangle, the resulting projecting corner of such rectangle would have the same height as .the centermost portion of the roof where the four sections Join.

From the two embodiments of the invention shown it will be apparent that the shell roof structure of my invention, while simple in form and application, is extremely Versatile architecturally in that almost any conceivable overall roof shape may be produced by its use. It is obvious, for example, that by merely changing the relative dimensions of FIG. 12 an oval shape can be produced. Also, by increasing or decreasing the twisting acti-on so Ias to increase or decrease the radius of curvature generated in the line defined lby FIG. 8, a different overall appearance may be created. It should be noted also that, generally speaking, the strength of the roof is increased by increasing the curvature; and the unsupported span of the roof may be increased using the same materials by increasing the curvature or, if desired, the number of overlapping sheets of corrugated material or the gauge thickness thereof may be decreased by increasing the radius of the curvature. In other words, the design desired :by the architect and the load to be carried must .be balanced suitably by the applica-tion of engineering principles. In the case lof the roof of my invention, stresses are relatively simply figured as contrasted with the shell structures used in the past.

It should be understood -that the overlapping sheets of corrugated material comprise the frame or structural portion of the roof of my invention, and this frame or structual portion may have any suit-able treatment common in the industry. Frequently corrugately aluminum and other such material may be left exposed because it has an adequate finished .appearance and will resist weathering without further treatment. Morevover, the overlapping corrugated materials `frequently furnish adequate insulation lwhere this is a factor. It should be understood, however, that the structural portion of the shell roof of my invention may be covered in whole or in part with any suitable material having an insulating, weather-proofing, decorative or the like function. 'In the case of some types of coating materials they may in themselves have some load-bearing or strength-imparting function.

In this connection I indicate -in FIG. 14 la section of roof comprising the overlapping members 221, 222 and 223 on which an upper coating 46 of roo-fing cement has been applied and which may be treated by the application of commonly employed insulating, reflective, and the like roofing materials. In FIG. 15, I also indicate the use of three overlapping sheets of material 3211, 322 `and 323 corresponding to similar corrugated sheets in the main embodiment but with a cement coating `47 formed entirely around, the top, bottom, and side edges of the roof structure comprising the three superposed members. A structure of this type is simply produced and, while it has the same appearance of a monolithic structure common to a poured cement shell, the structural portion -comprises the overlapping members characteristic of my invention; and the cement, while having some supporting eiect, is used primarily to obtain a desired architectural appearance.

I have referred to the overlapping sheets comprising the shell roof structure of my invention as corrugated sheet material. The important feautre `of corrugated sheet material is that it can be bent across the -corrugations without buckling and with the -application of relatively little force; while bending in a direction to deform the corrugations requires the application of much greater force and will be resisted by the sheet material until the corrugations themselves are actually deformed and broken down at the point `of bending, I have found that any sheet material having this property of being bendable in one plane and resisting bending in another plane may be -utilized for my purpose. While this characteristic is most simply and inexpensively obtained by corrugatinig sheet material with all the corrugati-ons running parallel to one another, any structural sheet material or composite of two or more materials having the property of bendability curvalinearly in one direction and resisting bending in a direction at -right angles to the rst-.dened direction may be readily used. I am therefore not limited in the practice of my invention to the use of corrugated .sheet nor to the use of any particular type of corrugation; and while my invention has been described in detail so that those skilled in the art may understand the manner of practicing the same, the scope of my invention is de-tined only by the claims.

I claim:

1. The method of producing a shell roof structure which comprises superposing two sheets of structural bendable material having undulations extending the length of each sheet with the undulations of the two sheets running at right angles to each other, rotating opposite edges of the sheets in opposite directions while said sheets are in mutual contact to define a composite structure generally approximating a hyperbolic paraboloid, and iixedly securing said sheets together at a plurality of contacting points of a plurality of Iche undulations of each sheet to retain said hyperbolic paraboloidal shape.

2. The method of producing a shell roof structure which comprises superposing two -sheets of corrugated metal with the corrugations of the two sheets` runnin-g at lright angles to each other, `rotating opposite edges of two sheets in opposite directions while said sheets are in mutual contact to deiine a composite structure generally `approxi-mating a hyperbolic paraboloid, and lixedly securing said sheets together at a plurality of contacting points of `a plurality of the corrugations of each sheet to retain said hyperbolic paraboloidal shape.

References Cited by the Examiner UNITED STATES PATENTS 32,256 5/186-1 Seely 52-618 2,093,836 `9/1937 Guyon 52-81 2,654,686 10/ 1953 Hansen 52-615 2,891,491 6/ 1959 Richter 5 2-81 2,912,940 11/1959 Baroni 52-80 FOREIGN PATENTS 1,159,357 2/1958 France.

781,162 8/1957 Great Britain.

EARL I. WITMER, Primary Examiner.

WILLIAM I. M-USHAKE, Examiner.

D. W. GRAVES, Assistant Examiner. 

1. THE METHOD OF PRODUCING A SHELL ROOF STRUCTURE WHICH COMPRISES SUPERPOSING TWO SHEETS OF STRUCTURAL BENDABLE MATERIAL HAVING UNDULATIONS EXTENDING THE LENGTH OF EACH SHEET WITH THE UNDULATIONS OF THE TWO SHEETS RUNNING AT RIGHT ANGLES TO EACH OTHER, ROTATING OPPOSITE EDGES OF THE SHEETS IN OPPOSITE DIRECTIONS WHILE SAID SHEETS ARE IN MUTUAL CONTACT TO DEFINE A COMPOSITE STRUCTURE GENERALLY APPROXIMATING A HYPERBOLIC PARABOLOID, AND FIXEDLY SECURING SAID SHEETS TOGETHER AT A PLURALITY OF CONTACTING POINTS OF A PLURALITY OF THE UNDULATIONS OF EACH SHEET TO RETAIN SAID HYPERBOLIC PARABOLOIDAL SHAPE. 